The Pittsburgh Post-Gazette is searchable for articles back to 1998. For articles back to 1990 use NewsBank--America's Newspapers, which you can get to by clicking on Databases at the top of this page and then navigating to the N section of the alphabetical listing. After you choose NewsBank, click on Pennsylvania, check Pittsburgh Post-Gazette, select your search terms, and run your search.
The Pittsburgh Tribune- Review includes searchable archive of back issues from 1988 - recent. Does not include photos for the back issues.
The Valley New Dispatch includes searchable archive of back issues, 1998 - recent. Same search engine used by the Tribune-Review.This site also includes links to many other smaller local weeklies. For older issues of the Valley News Dispatch on microfilm, go to the Community Library of Allegheny Valley in Tarentum. Their website gives their hours and directions: www.alleghenyvalleylibrary.org.
Articles from September of 2003 to current are available for free on the New Pittsburgh Courier website. For articles back to August 28, 1991, use the Ethnic Newswatch database. You can get to it by clicking on Databases at the top of this page and then navigating to the E section of the alphabetical list. Articles from 3/25/1911 to 12/28/2002 are available on the Courier website for a fee.